Search engines did not locate any advice for me, nor any way to ask for tech help with the website.
I also had trouble, a year or two ago, trying to email the IRS through their website, and finally figured out that the problem was that my favorite email address' URL has a hyphen (minus sign) in it, and that was being rejected as an illegal character. I tried the whitehouse.gov sign up again, using a phoneco/ISP variation of my email that has the same username and comes to the same account, but the URL has letters and (dot) only.
Success. I got my email with the new password almost immediately.
I figured I should post my discovery to help the next confused person searching for "no email whitehouse.gov".
By the way, the list of petitions is at
https://wwws.whitehouse.gov/petitions#!/petitions
It can be hard to find the log in at whitehouse.gov unless you go to the list or have a direct link to one of the petitions. The log in link is at the bottom right of the petition screens, in a dark blue bar, as of September 2011.
I encourage people to become politically concerned and active. Your fellow citizens need your responsible support. KGHN